Shannon was drafted by the Toronto Maple Leafs after only one season in the OHL. In his second season, he was awarded the Max Kaminsky Trophy as the OHL’s outstanding defenceman as well as being named a second all-star. His final season as a junior saw Shannon collect 83 points in only 60 games. As well as the Leafs, he played for the Winnipeg Jets, Buffalo Sabers, Atlanta Thrashers, Calgary Flames, and the Montreal Canadiens. Shannon played 544 regular season games in the NHL, scoring 28 goals and 111 assists for 139 points and collecting 523 penalty minutes. He would retire at the end of the ’01 season with the Montreal Canadiens.